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Re: Linked Data & RDFa

From: Gregg Kellogg <gregg@greggkellogg.net>
Date: Fri, 18 Jan 2013 10:19:41 -0500
To: Melvin Carvalho <melvincarvalho@gmail.com>
CC: Dan Brickley <danbri@danbri.org>, public-lod <public-lod@w3.org>
Message-ID: <DD4C7F88-A51C-4098-AFD3-75C354B038CE@greggkellogg.net>
On Jan 18, 2013, at 12:13 PM, Melvin Carvalho <melvincarvalho@gmail.com> wrote:

> On 18 January 2013 11:23, Dan Brickley <danbri@danbri.org> wrote:
> With RDFa maturing (RDFa 1.1, particularly Lite), I wanted to ask here
> about attitudes to RDFa.
> I have acquired the impression somehow that in the Linked Data scene,
> people lean more towards the classic 'a doc for the humans, another
> for the machines' partitioning model. Perhaps this is just a
> consequence of history; digging around some old rdfweb/foaf
> discussions[1] I realise just how far we've come. RDFa wasn't an
> option for a long time; but it is now.
> So - questions. How much of the linked data cloud is expressed in some
> variant HTML+RDFa alongside RDF/XML, Turtle etc.? When/if you do so,
> are you holding some data back and keeping it only in the
> machine-oriented dumps, or including it in the RDFa? Are you finding
> it hard to generate RDFa from triple datasets because it's 'supposed'
> to be intermingled with human text? What identifiers (if any) are you
> assigning to real-world entities? Dataset maintainers ... as you look
> to the future is RDFa in your planning? Did/does Microdata confuse the
> picture?
> I'm curious where we are with this...
> FWIW I personally use RDFa (+XHTML) on my homepage and as the basis for a distributed social network.  I'm happy to say at this point we can do pretty much everything except photos, but I expect that to happen Q1 of this year.
> RDFa (and RDFa lite) I think are unique in that they are data representations that the browser can click.  When you use curl or a programming language, you can set the MIME type.  With a browser, this is no longer true and you must accept the 'default'.  This makes HTML + data a compelling serialization.
> I'm not 100% up to date on the latest coming together of microdata and RDFa ... one important thing that RDFa allows is several subjects per page either absolute or relative (via # for example).  Does microdata have the same facility of dividing a document into sections via # and allowing you to add key value pairs?

Microdata allows you to specify the URL associated with an item using @itemid. I think that it's not used as much as @about or @resource is in RDFa, as few of the examples use this. More common is just using @itemscope, which results in BNodes being created; not great for linked data. Basically, while it's possible to do basic RDF in microdata (no typed literals, no control over RDF Collections), the result is more likely to be structured data with BNodes and possibly schema:url properties referencing related resources. Most users will never consider an RDF representation of their microdata, and be content with the JSON representation.

(all above just IMHO)


> Dan
> [1] http://lists.foaf-project.org/pipermail/foaf-dev/2000-September/004222.html
> http://web.archive.org/web/20011123075822/http://rdfwebring.org/2000/09/rdfweblog/example.html
Received on Friday, 18 January 2013 15:20:33 UTC

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